At present, binders which are commonly used for magnetic recording media include thermoplastic resins such as vinyl chloride-vinyl acetate resins, vinyl chloridevinylidene chloride resins, or acrylonitrile butadiene resins as described in, for example, U.S. Pats. Nos. 3,634,137, 4,409,291 and 4,409,299, and thermosetting resins such as melamine resins, urea resins or polyurethane resins as described in, for example, U.S. Pats. Nos. 4,049,871, 4,154,895 and 4,333,988. These binders can be used alone or in combination. However, the magnetic layer containing such conventional binders does not have good wear resistance. In addition, these binders often stain the tape path of the magnetic recording tape.
It is known to use a binder which is crosslinked by a chemical reaction, such as an isocyanate compound or an epoxy compound which can be added to the above-described thermoplastic resins as described in, for example, U.S. Pats. Nos. 4,333,988 and 4,411,956. However, these cross-linkable binders have the disadvantages that (1) the solution in which magnetic particles are dispersed has poor storage stability, which adversely affects the homogeneity of the magnetic coating composition as well as that of the magnetic recording tape and (2) heat treatment at a temperature of 50.degree. to 80.degree. C. for 1 to 5 days is required to harden the magnetic recording layer after it is coated and dried, requiring a long period of time.
A magnetic recording tape which can be used for recording for an extended period of time has recently been developed and must withstand use under harsh conditions. For this purpose, the support should be thin and the mechanical properties of the magnetic layer should be improved. A method has been proposed to accomplish this purpose in which an oligomer or a monomer of acrylates is used as a binder and is hardened by electron beam radiation after it is dried, as disclosed in Japanese Patent Application (OPI) No. 25231/81 (the term "OPI" as used herein refers to a "published unexamined Japanese Patent Application") corresponding to U.S. Pat. No. 4,443,490. However, a magnetic recording medium having both excellent electromagnetic properties and excellent mechanical properties has not yet been developed.